M3 has the following differences:
- Nappa leather
- Slightly smaller and chunkier
- 'DCT' paddles
135 and M3 steering wheels are interchangeable though. In fact, all E8x and E9x (with the later model 'round' airbag) are interchangeable with each other and/or the M3.
The only steering wheel that has some complications is the 'LCI' steering wheel found on the LCI E92s and N55 135s. These LCI paddles require some modification before working on a pre-LCI car.
1M steering wheels are the same as (manual) M3 steering wheels. These are only suitable for manual cars. You could put one on an Auto car but you would lose your paddle functionality.